Replaceable hammer tip for hammer mills



Sept. 13, 1966 w. w. WELLER REPLAGEABLE HAMMER TIP FOR HAMMER MILLS 2 SheetsSheet 1 Filed Aug. 15, 1963 Inventor ward W. Weller 132, wallaeafi q D fHfornew Sept. 13, 1966 w. w. WELLER 3,272,445

REPLACEABLE HAMMER TIP FOR HAMMER MILLS Filed Aug. 15, 1963 2 Sheets-Sheet 2 Inventor Ward W. Weller B2 Mae/m, MDW

v 'ltornegs United States Patent 3,272,445 REPLACEAIBLE HAMMER TIP FUR HAMMER MILLS Ward W. Weller, 25 Benvenue St, Wellesley, Mass. Filed Aug. 15, 1963, Ser. No. 302,411 Claims. (Cl. 241-197) This invention relates to a replaceable hammer tip and more particularly to a replaceable hammer tip of the type employed in a hammer mill.

In a conventional hammer mill, hammers equipped with replaceable tips are rotated about a central axis within the interior of the mill and the tips impinge against coarse material charged into the mill resulting in comminution of the charge.

It will be realized that the tips of the hammers are subjected to extreme forces and undergo significant wear which decreases their efiiciency with use, and it therefore is an object of the present invention toprolong the efficiency of a hammer tip by associating therewith inserts of a material harder than the material of which the hammer tip is composed so that the rate of wear is materially reduced as the hammer head undergoes wear, the inserts being so positioned as to resist development of what is observed to be the normal wear pattern of the hammer tip.

A further object of the invention is to increase the efficiency of a hammer tip and thereby the hammer mill by so constructing the geometry of the hammer tip that its action as a flail or slinger for slinging the material against the walls of the hammer mill is increased. More specifically, in accordance with a further object of the invention, the efiiciency of a hammer mill is increased by providing the hammer tips with a concave scoop or centrifugal pocket which more readily traps the charge and more effectively throws the charge to be comminuted against the walls of a hammer mill.

The leading part at the bottom of the leading wall of the hammer tip receives the most wear and has in the past been a blunt point. A further object of the invention is to provide a hammer tip with a sharp, pointed leading point which work hardens more rapidly under the repeated blows than a blunt point. A more specific object of the present invention is to afford a finer or thinner leading edge by having a concave face of a centrifugal pocket flare into convex bottom wall to produce a less than 90 corner and a finer leading point or edge.

Other and further objects of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawings, which, by way of illustration, show a preferred embodiment of the present invention and the principles thereof and what is now considered to be the best mode contemplated for applying these principles. Other embodiments of the invention embody the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention.

In the drawings:

FIG. 1 is a perspective view of the hammer tip constructed in accordance with the preferred embodiment of the invention;

FIG. 2 is a plan view of the hammer tip with a portion broken away in section;

Patented Sept. 13, 1966 FIG. 3 is a front elevational view of the hammer tip constructed in accordance with the preferred embodiment of the invention;

FIG. 4 is a sectional view taken along the line 4-4 in FIG. 3 in direction of the arrows showing the cavities in the hammer tip casting;

FIG. 5 is a partial section view showing the attachment of the hammer tip to a shank of a hammer mill;

FIG. 6 is a sectional view showing a tool steel insert within a recess in the hammer tip.

Referring now to the drawings, and more particularly to FIG. 1, the hammer tip 10 is shown as a one-piece body 11 of cast manganese steel having an overall boxlike shape with curved walls. The hammer tip 10 is preferably made of a cast manganese steel alloy as manganese steel alloys tend to become harder under repeated impacts, and since it has sufficient tensile strength to withstand shock impacts which would break a more brittle cast material.

As shown, the hammer tip it) has top border walls 12 which define a generally fiat, horizontal surface, FIG. 3, and a larger central opening 14, FIGS. 1 and 2. As seen in FIGS. 1 and 2, the hammer tip 10 has a pair of side walls 20 and 22, each of which has a convex top portion 23 having its highest and medial point 25 tangential to the plane of the top surface of walls 12. The side walls 20 and 22 terminate in a convex bottom wall or surface 27 which has central groove 28 medially disposed on the bottom surface 27 and extending across from the side wall 20 to the side wall 22, as indicated by the dotted lines in FIG. 2.

The tip 10 inciudes vertically extending front and rear working edges 3t) and 31 which are of a concave nature and which, respectively, define the boundaries of a pair of opposed concave surfaces constituting the end walls 32 for the hammer tip 10. The end walls 32 extend from a lower edge 35 and curve inwardly and upwardly to an upper edge 36. The end walls 32 are identical and the hammer head it) is rotated 180 to reverse the positions of the end walls 32 when one of the leading end walls becomes more worn than the other one.

Each one of the end walls 32 serves as a centrifugal pocket, but only one end wall 32 is effective at any one time, which one is effective, depends upon the direction in which the hammer tip is rotated. The end walls 32 act as centrifugal pockets in that the leading end wall 32 functions to collect or trap portions of the charge fed to the mill and then to sling the material outwardly against the walls of the hammer mill. The materiai is broken by hard liner inserts attached to the walls of the mill. The overall efliciency of the hammer mill is considerably increased by the provision of the scoops or fiails formed by the concave surfaces 32 which are more effective in gathering and flinging the material against the walls than would be a flat planar surface.

The edges 35 at which the concave surfaces of the end walls 32 join the bottom walls 27 of the hammer tip 10 are the leading corners or edges of the hammer tip 10, only one edge at a time being a leading edge in that it precedes the body 11 of the hammer in the direction of rotation. The juncture between the bottom wall 27 and the end wall 32 defines a sharp point or corner for the leading edge 35 as contrasted with a conventional blunt corner, of or more, and which was often rounded at the leading edge. That is, the leading point or edge 35 is at a corner defined by the juncture of the bottom wall 27 and end wall 32 and which corner is less than the conventional 90 and is a wedge or triangular shaped in section. The sharper point of the leading edge 35 of the hammer tip casting 11 provides a surface of manganese steel that work hardens more quickly with successive impact blows engendered by contact with the charge than would the more blunt point of a conventional hammer. Hence, even though of a thinner cross section, the pointed leading edge will resist wear because it hardens more rapidly than a blunt section. Thus, the concave central pocket not only affords a manner of increasing the throwing of material against the side walls, but also affords a manner of flaring into a finer point or leading edge, which work hardens very quickly.

As the hammer head is subjected to continual operation the Walls 32 are subjected to wear. The observed pattern of wear is shown in FIG. 6 by the dotted line 44 and the dotted line progressively moves toward the diagonally, opposite, upper corner of the hammer as the hammer tip wears away. This wear is due mainly to attrition by abrasion of the leading edge grinding and a'brading the charge against the walls of the mill.

To increase the effectiveness of the hammer, after the edge wears away for a slight distance, the hammer tip is provided with strategically placed tool steel inserts 40, FIG. 6, one of which is shown positioned within a recess 41 of the hammer tip 10. As seen in FIGS. 3 and 6, the cavity 41 and tool steel insert lie on the wear path from their respective leading edges 35 so that as their respective leading edges wear back, the leading edge 43 of the tool steel insert becomes effective as the leading edge and bears the brunt of abrading the charge.

The tool steel insert 40 can be of any one of a number of suitable hard materials. Preferably, a tool steel insert of tungsten carbide is used, which, although not having the resistance to shock of the manganese steel body 11, has a harder composition which resists attrition due to wear better than does the softer work hardenable alloy. Thus, when a normal hammer tip is becoming less efficient and wearing away more rapidly, the present hammer tip arrests this trend with a hard tool insert 40 which retards further wearing away and provides a better abrasion resistant surface. The tool steel inserts 40 can be placed in a mold and have the manganese steel casting body 11 cast thereabout or the manganese steel body 11 can be formed with the cavities 41 shown in FIGS. 1 and 3, after which a tool steel insert of a complementary size and shape can be inserted and held in place within the cavity by press fitting or mechanical attaching means. Also, it is to be understood that the hammer tip 10 is symmetric about a medial axis, and that when a leading edge 35 and tool steel insert 40 become worn that the hammer tip 10 can be rotated 180, whereby the other and opposite leading edge 35 and tool insert 40 are brought into effective material breaking position.

For the purpose of securing the hammer tip in the hammer mill, the hammer tip 10 has a plurality of aligned openings in each of the side walls 20 and 22, which connect with the center opening 14. As seen in FIG. 5, the hammer tip 10 can be attached to a shank by placing the opposed pair of bars 56 of the shank in a horizontal position shown in phantom lines wherein the claws 57 are positioned with the points of the claws 57 extending downwardly into the central cavity 14. Then, by rotating the bars 56 to a vertical position where the bars 56 abut one another, the claws 57 are hooked in the cavities 50 and support the hammer tip 10.

The bars 56 are secured together by a bolt 58 and a nut 59 seated in pockets on the respective bars 56. The upper ends of the bars 56 are formed with enlarged, cylindrical bosses 60 which have aligned horizontal bores 61 therein to receive a supporting shaft (not shown) of a hammer mill. The claws 57 and the recesses 50 are a conventional manner of attaching a hammer tip and 4. do not form a part of this invention. It is to be understood that other suitable manners of connecting the hammer tip 10 to a hammer mill could be employed equally as well.

From the foregoing, it is apparent that the concave pocket formed by the concave end walls 32 serve to provide an increased and more effective manner of throwing the material against a side Wall of the hammer mill, and that the concave end walls flare to a finer leading point or edge which will more rapidly work harden than a less pointed leading edge when the tip is composed of manganese steel or similar work hardenable ferrous alloy. Also, it should be apparent that the effectiveness and efficiency of the present hammer tip 10 is enhanced since a wearing away of the leading edge 35 thereof exposes a hard tool steel insert 40 which retards the rate of wearing away.

Hence, while preferred embodiment of the invention has been described and illustrated, it is to be understood that this is capable of variation and modification.

I claim:

1. A replaceable hammer tip adapted to be secured in a hammer mill where coarse material is comminuted to a fine size by being struck by the hammer tip and by being thrown against the walls of the hammer mill, comprising a main body member having a top wall, a bottom wall, side walls and end walls; said end walls being the surfaces for striking the material being broken, said end walls having concave surfaces thereon for scooping the material and flinging the material against the side walls of the hammer mill, said bottom wall being of a convex configuration, said convex bottom wall extending across said body to said side walls to uninterrupted lower leading edges with the respective end walls, corners being formed by the intersection of said convex bottom wall and said concave surfaces of said end walls, said corners being less than said concave surfaces flaring upwardly and toward each other from said uninterrupted leading lower edges and then flaring upwardly and then outwardly from each other to form upper leading edges disposed substantially in the same planes as their respective lower leading edges.

2. A replaceable hammer tip adapted to be secured in a hammer mill wherein coarse material is broken to a finer size by being hit with a hammer tip and being thrown against the sides of the hammer mill comprising a main body member formed of a work hardenable ferrous alloy, said body member having end walls and a bottom wall meeting in a leading edge adapted to receive the greatest amount of wear during rotation of the hammer tip in the hammer mill; a seating means in the main body member adjacent the leading edge of the body member; and a metallic insert seated in said seating means, said insert being of a harder material than the metal of the main body member so that as the leading edge of the main body member is worn away, the insert becomes effective to provide a harder surface for continued breaking of the coarse material.

3. A replaceable hammer tip adapted to be secured in a hammer mill where coarse material is comminuted to a fine size by being struck by the hammer tip and being thrown by the hammer head against the side walls of the hammer mill, comprising a main body member formed of a cast metal; a pair of opposed end walls on said body member having a concave configuration thereon for scooping material as the hammer tip is rotated and for throwing the material against the walls of the hammer mill; a bottom wall of said body member joining said end walls to form a leading edge which bears the brunt of the wear during the braaking of the coarse material; and an insert of a second material having the capacity of resisting wear disposed in said body member adjacent the leading edge whereby as the leading edge wears away, the insert is exposed to bear the brunt of the breaking of the coarse material.

4. A replacement hammer tip adapted to be secured in a hammer mill where coarse material is broken into a finer size comprising a main body member formed of a cast material; a plurality of concave end walls on said body member for scooping the material therein, and for throwing the material against the walls of the hammer mill; a convex bottom wall on said hammer joining said concave end walls to produce less than 90 corners which act as the leading corners bearing the brunt of the abrasion and wearing forces; and inserts of a second material disposed in said body member adjacent the leading corners whereby upon wearing away of the leading corners the inserts are exposed to bear the brunt of the impingement against the material.

5. The hammer tip of claim 4 wherein said cast material is a manganese steel alloy said second material is tungsten carbide.

References Cited by the Examiner ROBERT C. RIORDON, Primary Examiner.

H. F. PEPPER, Assistant Examiner. 

1. A REPLACEMENT HAMMER TIP ADAPTED TO BE SECURED IN A HAMMER MILL WHERE COARSE MATERIAL IS COMMINUTED TO A FINE SIZE BY BEING STRUCK BY THE HAMMER TIP AND BY BEING THROWN AGAINST THE WALLS OF THE HAMMER MILL, COMPRISING A MAIN BODY MEMBER HAVING A TOP WALL, A BOTTOM WALL, SIDE WALLS AND END WALLS; SAID END WALLS BEING THE SURFACES FOR STRIKING THE MATERIAL BEING BROKEN, SAID END WALLS BEING CONCAVE SURFACES THEREON FOR SCOOPING THE MATERIAL AND FLINGING THE MATERIAL AGAINST THE SIDE WALLS OF THE HAMMER MILL, SAID BOTTOM WALL EXTENDING ACROSS CONFIGURATION, SAID CONVEX BOTTOM WALL EXTENDING ACROSS SAID BODY TO SAID SIDE WALLS TO UNINTERRUPTED LOWER LEADING EDGES WITH THE RESPECTIVE END WALLS, CORNERS BEING FORMED BY THE INTERSECTION OF SAID CONVEX BOTTOM WALL AND SAIDS CONCAVE SURFACES OF SAID END WALLS, SAID CORNERS BEING LESS THAN 90*, SAID CONCAVE SURFACES FLARING UPWARDLY AND TOWARD EACH OTHER FROM SAID UNINTERRUPTED LEADING LOWER EDGES AND THEN FLARING UPWARDLY AND THEN OUTWARDLY FROM EACH OTHER TO FORM UPPER LEADING EDGES DISPOSED SUBSTANTIALLY IN THE SAME PLANES AS THEIR RESPECTIVE LOWER LEADING EDGES. 